Heat exchanger

ABSTRACT

A heat exchanger having an externally finned pipe in which a first heat exchanger fluid flows, with the fins lying in a plane essentially perpendicular to the axis of the pipe, a length of said finned pipe being enclosed within a casing so that the walls of the casing are essentially adjacent to the fins at least at two opposed generating lines, and the inner space of said casing serving for the flow of a second heat exchange fluid, whereby the latter is compelled to flow substantially at a right angle to the axis of said pipe.

1451 Apr. 9, 1974 United States Patent Garcea 293,245 l2/l953Switzerland.........................I65/l54 Inventor: Gianpaolo Garcea,Milan, Italy Alfa Romeo S.p.A., Milan, Italy July 27, 1972 Appl. N0.:275,880

[73] Assignee:

[22] Filed:

Primary Examiner-Charles .l. Myhre Assistant Examiner-Theophil W.Streule, Jr. Attorney, Agent, or Firm-Holman & Stern [57] ABSTRACT Aheat exchanger having an externally finned pipe in which a first heatexchanger fluid flows, with the fins [30] Foreign Application PriorityData July 27, 1971 7739/71 lying in a plane essentially perpendicular tothe axis of the pipe, a length of said finned pipe being enclosed withina casing so that the walls of the casing are es- 165/154, 160, 163, I68,169 sentially adjacent to the fins at least at two opposed generatinglines, and the inner space of said casing References cued serving forthe flow of a second heat exchange fluid, UNITED STATES PATENTS wherebythe latter is compelled to flow substantially at 3/1964 a right angle tothe axis of said pipe. 4/1936 12/ 1933 165/74 165/75 Behringer et al.165/72 3,124,122 Baron 2,039,066 De Weese............. 1,939 160 3Claims, 9 Drawing Figlres PATENTEBAPR 9:974 3802499 m 1or3 ze I 25PAIENTEUAPR 91914 SHEET 3' [IF 3 HEAT EXCHANGER BACKGROUND OF THEINVENTION In heat exchangers between two different fluids A and Bseparated by a wall, if the heat exchange through convection betweenfluid A and the wall is more difficult than that between the wall andthe fluid B, for example because of the greater viscosity of the fluidA, the solution is well-known of resorting to a separation wall that hasa more extensive surface in contact with fluid A than that in contactwith fluid B. This is achieved for example by equipping the surface incontact with fluid A with fins; particularly providing a pipe throughwhich fluid B flows with external fins lapped by fluid A. But theefficiency of a heat exchanger using a pipe of this type is rather lowif fluid A, through increased viscosity due to cooling, ceases to flowwithin the spaces between the adjacent fins and the subsequent fluidpasses over this non-moving stratum without coming into contact with thefinned surface and without appreciably being cooled.

OBJECT AND SUMMARY OF THE INVENTION The object of this patentapplication is to achieve a heat exchanger using a pipe finnedexternally, with the direction of the fins being essentiallyperpendicular to the axis of the curve generated by the pipe, throughwhich condition the velocity of the fluid A is activated in theabove-mentioned spaces, and thus the thermal exchange is substantiallyimproved as a result of this activation of the velocity. It is obviousthat an external energy is required for this activation to offset theload losses of either viscous or turbulent type, energy furnished toliquid A by a circulating pump; but the proportioning of the proposedexchanger can be made op-- timal in the individual case so asnot torequire an excessive head which can therefore be taken care of with anormal circulation pump. The advantages of the exchanger according tothis invention, in relation toa conventional exchanger, consist first ofall in a decisive reduction in the exchange surface required andtherefore in the weight, dimensions and cost; but also in a greaterquickness of response since the thermal inertia .of the exchangeraccording to the invention is rather low; further, in this exchanger thedanger of leaks of one of the fluids into the other through theseparating wall is avoided; a further characteristic of the presentexchanger is, in fact, that of using a finned pipe through which fluid Bflows located within a casing, while fluid A within said casing flows onthe outside of the finned pipe; the finned pipe being constructed inaccordancewith current technology in a single piece and without welding,internal leaks are impossible; the only possibility for leakage of fluidA would be toward the exterior I at the point where the two ends of theabovementioned pipe pass from the interior of the casing to theexterior; a possibility which, for that matter, can be easily excludedby using, for example, rubber or synthetic seals.

increase in the power absorbed by the circulating P p- The proposedsolution produces an improvement in the thermal exchange between thefluids not only because the increase in velocity of fluid A prevents thedanger of non-flow, but also because, fluid A being obliged to passpredominantly within the spaces between the fins, the reduction ofthickness of the fluid current which laps the finned surface assures anefficient cooling of the entire contents. In fact, in laminar flow thecooling of the various borders or fillets by fluid A occurs throughconduction and the fluid borders which cool by contact with the finnedsurface cool those of the over-lying strata all the more rapidly thesmaller the thickness of the fluid mass. From that comes the possibilityof reducing the distance of flow of fluid A and therefore the dimensionsof the exchanger inasmuch as the dwell time is diminished, that is, thetime necessary for the parts of the fluid borders cooled by the finnedwall to cool through contact with the over-lying ones.

With a finned pipe having a rectilinear course within the casing andwith a casing having a substantially parallelepiped form, the twoopposing walls of the casing which adhere to the crest of the fins canbe flat and essentially parallel; but, in order for fluid A to be guidedbetween the spaces of the fins for a greater distance, it is well forthe two opposing walls of the casing to adhere to the crest of thefinning of the pipe for a discrete distance along the circumferentialline of the crest of the finning; in this case, in the zone of contactwith the crest of the finning, the surface of the casing assumes anessentially cylindrical form coaxial with the axis of the finned pipe.

The same result is obtained if, in the spaces between the flat walls ofthe casing and the crests of the fins of the pipe (where the crests arenot near the walls) there are placed elements shaped essentiallytriangularly (with the sides of the triangle possibly curved) with anaxis having a course parallel to the axis of the finned pipe.

In reference to the extent of the capacity and thermal exchange desired,a modification foreseen for the exchangers above-described can beadvantageous; within thecasing which contains at least one finned pipe,there can be arranged suitable deviating baffles perpendicular to theaxis of the pipe itself (possibly obtained by modifying only the form ofthe casing), placed above and below the pipe in the direction of flow offluid A and conveniently staggered, so that fluid A is compelled to lapsuccessively various zones axially adjacent to the finned pipe followingan essential sinusoidal or better a zig-zag course.

Due to its characteristics, the exchanger according to the invention hasproved to be suitable in many installations, but particularly inmotor-vehicles, in which it is necessary to effect a heat exchangebetween the lubricating oil and the cooling water of the motor, andwhere it can happen that spaces of particular form or dimensions areavailable in which it would be impossible to install a conventionalexchanger which is too big and too heavy.

The exchanger according to the invention is composed of a pipe in whichthe first of said liquids flows and which is equipped with externalfinning lying in a plane essentially perpendicular to its axis, saidpiping having one of its sections contained within a casing whose wallis essentially adjacent to said finning at least at the point of twoopposite generated lines of said piping, the space enclosed within saidcasing constituting the passage for the second of said liquids whichmoves within said casing principally in a direction at a right angle tosaid piping.

The advantages and characteristics of the exchanger according to theinvention will be better understood from the possible embodiments of theinvention illustrated in the attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view taken along line IIof FIG. 2;

FIG. 2 is a view taken along line IIII of FIG. 1;

FIG. 3 shows a modified exchanger along line III--III of FIG. 4 insection along line IIIIII of FIG. 4;

FIG. 4 is a view taken along line IVIV of FIG. 3;

FIG. 5 is a view in section along line VV of FIG.

FIG. 6 shows an axial cross-section of an exchanger constructed with afinned pipe having it axis wound in spiral form;

FIG. 7 is a partial view along line VIIVII of FIG. 6;

FIG. 8 is a part of an axial section of a variation of the exchanger ofFIG. 6; and

FIG. 9 is a part of an axial section of the exchanger of FIG. 6 furthermodified.

DETAILED DESCRIPTION OF THE EMBODIMENTS In FIGS. 1 and 2 are indicated afinned pipe 10, with the direction of the fins being perpendicular tothe axis of the pipe constructed in a single piece and, in thisparticular instance, shaped in the form of a U, a casing 11 contains thefinned pipe, and 12 and 13 denote the smooth terminal parts of the pipe,outside the casing, to which are attached with seals the inlet anddischarge pipes respectively of the cooling fluid B, and the pipes arenot shown in the figures. Indicated l4 and 15 are the two finnedbranches with a rectilinear axis inside the casing and 16 the connectingelbow between the two branches outside bottom wall 17 of the casing, andthe elbow is also preferable smooth. Casing 11 has one wall, indicated18, which is movable, suitable for facilitating the cleaning operations,consisting of a flange joined in a conventional manner (not shown) tothe corresponding counter-flange of the body of the casing using anin-between gasket 38. The two branches l4 and 15 are welded to the wall17 of the casing and conne cted with a gasket seal to flange 18 by meansof rings 20 and 23 at the point of passage from the inside of the casingto the outside.

In wall 22 is machined a hole in which inlet pipe 21 is welded for thecooling of fluid A, and in wall 19 a hole in which is welded the outletpipe for fluid A.

Arrows 25 and 26 indicate the direction of the flow of fluid B withinthe finned pipe 10, arrows 27 and 28 indicate the direction of movementof the fluid A within the casing 11 where it is effectively cooled sincewalls 29 and 30 of the casing adhere to the crests of the finned pipe,and the fluid is forced to pass predominantly within the spaces betweenthe fins.

In fact, walls 29 and 30 of the casing 11 are formed in the zone ofcontact with the crests of the fins of the pipe 10 so as to assume anessentially cylindrical form coaxial with the axis of each of the twobranches l4 and 15 with the advantage that, fluid A being guided between the spaces within the fins for a more extensive distance, a goodheat exchange between fluid A and fluid B is achieved.

The exchanger shown in FIG. 3 is constructed with a pipe 32 consistingof a single finned section 37 inserted within a casing 39; finned pipe32 has its end parts 33 and 34 smooth extending outside of walls 35 and36 respectively of casing 39; seal rings 45 and 46 are located at thepoint of passage from the inside of the casing to the outside. The inletand discharge pipes of fluid B joined to ends 34 and 33 of the finnedpipe are not shown, but arrows 41 and 40 indicate the direction of flowof fluid B within the finned pipe 32.

The walls of casing 39 are shaped in the zone of contact with the crestsof the fins of the section 37, so as to assume an essentiallycylindrical form coaxial with the axis of the finned section, andcontain recesses 42 through which they adhere to the crests of the finsblending with the waved zones, but predominantly remain away from thecrests of the fins so as to form the cavities indicated with 53.

FIGS. 4 and 5, which show two views of the exchanger, sectionedrespectively along lines IV-IV and VV of FIG.3, clarify the detailedform of the casing.

To the walls of the casing are welded pipes 43 and 44 for the inlet andoutlet of fluid A, with arrows 47 and 48 indicating respectively thedirection of movement of fluid A at the inlet of the casing and at theoutlet of same.

The alternating of cavities and recesses in the walls of the casing,located in the axial direction and suitably baffled, obliges fluid A towash against the finned surface of pipe 32 following a sinusoidal orbetter a zig-zag course, as indicated by arrows 49 and 50, that is,after fluid A has washed against the finned surface of a first sectionof pipe, flowing within the spaces between the fins as indicated byarrows 51 and 52 of FIG. 4, it is conveyed from the cavity 53 toward thesubsequent section of the pipe and obliged to How again within thespaces of the fins.

This exchanger was achieved as a pipe having a single finned section,but naturally one could use, as in the previous constructions, aU-shaped pipe with deviating or diverging branches installed within thecasing suitably baffled which could oblige the fluid to flow onto thefinned surfaces of the pipes in a zig-zag course. Exchangers based onthe same structural concepts can be achieved with several finnedbranchesinstalled within the casing using either one pipe in the form ofa coil or several pipes equipped with an inlet manifold and an outletmanifold for fluid B.

In FIG. 6, 54 indicates the finned pipe with the fins extendingperpendicularly to the axis generated by the pipe itself, as is clearlyshown in FIG. 7; 59 and indicate its ends which are smooth, and in thisconstruction the pipe in its finned portion has its axis wound in 'aspiral in closed-coil fashion; 55 indicates a casing which contains afinned pipe, 56 the external cylindrical wall,

57 an internal cylindrical wall, and 58 a circular wall having a wholeand which is integral with the cylindrical wall 57.

61 and 62 indicate two end covers in which are machined holes 77 and 78(with the respective recess for seal rings 87 and 88) for the passage ofthe smooth ends 59 and 60 of the finned pipe 54 from the inside of thecasing 55 to the outside, and 79 and 80 indicate threaded holes in whichare screwed, with previous placement of seal washers 83 and 84, inletand outlet fittings 81 and 82 for the fluid A to be cooled. Fluid Bflows within finned pipe 54 in the direction indicated by arrows 86 and85.

In covers 61 and 62 are further machined coaxial holes 63 and 64; 66indicates a tie-rod, threaded at both ends, 67 and 68, inserted in holes63 and 64 of the covers and in hole 65 of circular wall 58 with theinterposing of two spacers 69 and 70, which tie-rod serves to secure thevarious components of the exchanger. A nut 71 is screwed on threaded end67 and nut 72 on threaded end 68 there having been inserted previouslybetween the nuts and the'covers, washers 73 and 74 which assure a goodseal at the points of the holes 63 and 64. For the purpose of avoidingleakages of the fluid A toward the outside, two rings of elasticmaterial 75 and 76 are installed between the wall 56 and the covers 61and 62.

Arrows 89 and 90 indicate the direction of flow of fluid A at the inletand outlet of casing 55.

Fluid A which flows within the casing in the space contained between thetwo walls 56 and 57 in a direction parallel to the lines generated bythe cylindrical walls is obliged to pass predominantly within the spacesbetween the fins and therefore to wash against the finned surfaces ofthe pipe becoming substantially cooled within a limited space.

In the further variants of the exchanger, shown in FIGS. 8 and 9, thesame numbers indicate the parts that are analogous to those of theexchanger of FIGS. 6 and 7; in the first embodiment, two elements 91 and92 are visible shaped with a triangular cross-section with the sides ofthe triangle curved arranged with the axis wound in the form of a coilparallel to the axis of the finned pipe. The abovementioned elements,inserted in the spaces between the walls 56 and 57 of the casing and thecrests of the fins of pipe 54, oblige fluid A to flow within the spacesof the fins, guiding it through a larger area, with a furtherimprovement of the heat exchange, an advantage which is obtained also inthe case of the exchanger shown in FIG. 9, in which 93 and 94 indicatethe external and internal walls of the casing of finned pipe 54, whichare cylindrical surfaces in the form of waves, with the course of thewaves being spiral and parallel to the course of the axis of the coiledfinned pipe.

What I claim is:

l. A heat exchanger for heat exchange between two liquids, one of whichliquids is viscous, including a cylindrical casing having an innersurface, an inner cylindrical member of lesser diameter than the casingwithin the casing and having an outer surface, said casing beingprovided with an inlet and an outlet for the viscous liquid, a finnedtubing within the casing, said tubing having inlet and outlet ends, thetubing having outer fins lying in a plane perpendicular to the axis ofthe tubing, said tubing being helically wound with closely adjacentturns to provide a cylindrical assembly, the other liquid flowing insidethe tubing from the inlet to the outlet, and the turns of the tubingbeing at least partially but not completely enclosed between the innersurface of the casing and the outer surface of the cylindrical member sothat the outer contours of the fins are adjacent said surfaces therebycompelling the viscous liquid to flow through the passages definedbetween the fins of the tubing, thus preventing stagnation zones frombeing formed and maintaining the heat exchange at the optimum level.

2. The heat exchanger as claimed in claim 1 in which between the innersurface of the casing and the outer surface of the cylindrical memberand the crests of the fins are located elements triangular in crosssection, with the sides of the cross section following a helical pathparallel to the axis of the wound tubing.

3. The heat exchanger as claimed in claim 1 in which the inner surfaceof the casing and the outer surface of the cylindrical member are shapedto provide a helical path parallel to the course of the axis of thewound tubing.

1. A heat exchanger for heat exchange between two liquids, one of whichliquids is viscous, including a cylindrical casing having an innersurface, an inner cylindrical member of lesser diameter than the casingwithin the casing and having an outer surface, said casing beingprovided with an inlet and an outlet for the viscous liquid, a finnedtubing within the casing, said tubing having inlet and outlet ends, thetubing having outer fins lying in a plane perpendicular to the axis ofthe tubing, said tubing being helically wound with closely adjacentturns to provide a cylindrical assembly, the other liquid flowing insidethe tubing from the inlet to the outlet, and the turns of the tubingbeing at least partially but not completely enclosed between the innersurface of the casing and the outer surface of the cylindrical member sothat the outer contours of the fins are adjacent said surfaces therebycompelling the viscous liquid to flow through the passages definedbetween the fins of the tubing, thus preventing stagnation zones frombeing formed and maintaining the heat exchange at the optimum level. 2.The heat exchanger as claimed in claim 1 in which between the innersurface of the casing and the outer surface of the cylindrical memberand the crests of the fins are located elements triangular in crosssection, with the sides of the cross section following a helical pathparallel to the axis of the wound tubing.
 3. The heat exchanger asclaimed in claim 1 in which the inner surface of the casing and theouter surface of the cylindrical member are shaped to provide a helicalpath parallel to the course of the axis of the wound tubing.